package leetcode._0275;

/**
 * 275. H-Index II
 * Medium
 *
 * 232
 *
 * 414
 *
 * Favorite
 *
 * Share
 * Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index.
 *
 * According to the definition of h-index on Wikipedia: "A scientist has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each."
 *
 * Example:
 *
 * Input: citations = [0,1,3,5,6]
 * Output: 3
 * Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had
 *              received 0, 1, 3, 5, 6 citations respectively.
 *              Since the researcher has 3 papers with at least 3 citations each and the remaining
 *              two with no more than 3 citations each, her h-index is 3.
 * Note:
 *
 * If there are several possible values for h, the maximum one is taken as the h-index.
 *
 * Follow up:
 *
 * This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
 * Could you solve it in logarithmic time complexity?
 * Accepted
 */

/**
 * https://leetcode.com/problems/h-index-ii/
 */
public class Solution {

    /**
     * log(n)的时间就只能二分了
     * @param citations
     * @return
     */
    public int hIndex(int[] citations) {
        int left = 0, len = citations.length, right = citations.length - 1, mid = 0;
        while (left <= right) {
            mid = (left + right) >> 1;
            if(citations[mid]== (len-mid)) return citations[mid];
            else if(citations[mid] > (len-mid)) right = mid - 1;
            else left = mid + 1;
        }
        return len - (right + 1);
    }
}
